export function throttle(fn, interval) {
  var last
  var timer
  return function() {
    var th = this
    var args = arguments
    var now = +new Date()
    if (last && now - last < interval) {
      clearTimeout(timer)
      timer = setTimeout(function() {
        last = now
        fn.apply(th, args)
      }, interval)
    } else {
      last = now
      fn.apply(th, args)
    }
  }
}
